Bryan goes over the HVAC troubleshooting mindset, including the 5 Pillars of diagnosis, at an HVAC training class in Birmingham, AL. He also covers a few mental shortcuts you can take that still allow you to troubleshoot accurately.
Good troubleshooters and diagnosticians listen a lot more than they talk. Troubleshooting requires us to find the problem and solve it, but the best diagnosticians figure out WHY the problem exists in the first place and takes steps to rectify the problem's source.
The 5 Pillars are five measurements that tell us a LOT about an HVAC system's performance. (Believe it or not, static pressure is not on there. We technically could add delivered capacity, too.) You CAN use non-invasive testing to check the 5 Pillars, and you can use it to set the charge. The point of the 5 Pillars is to avoid setting the charge by just ONE value; that's just not a reliable practice when you have load changes and variations in performance.
We currently have newer, more accurate ways of finding airflow and delivered capacity. (Those methods surely beat using a lot of math and a thermocouple covered in a sock soaked with distilled water!) Nowadays, delivered capacity could potentially be more useful than one of the original 5 Pillars, delta T.
The other 5 Pillars include suction pressure, head pressure, superheat, and subcooling. However, suction and head pressure could easily be replaced by saturation and condensing temperature. The most important thing is to make a quick "if-this-then-that" mindset for troubleshooting, and having a set of 5 Pillars is a way to use heuristics (mental shortcuts) to your advantage in the field.
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/.